This invention relates to optical resonators and instruments incorporating the same and, more particularly, to an optical resonator having a high Finesse.
An optical resonator basically is a device which supports circulation, e.g., oscillation, of optical radiation in a sustaining fashion. That is, in a stable resonator every time optical radiation returns in space to a particular point when enough power is supplied to overcome decay due to internal losses, the phase and amplitude of the radiation are the same as the previous occasion. In this way, when a stable resonator is driven for a time longer than the circulation time, amplitude constructive interference occurs with consequent strong coupling between the driving mechanism and the resonator. This constructive interference is called resonance. (The term "optical radiation", as used herein, means electromagnetic radiation in the visible wavelength spectrum and in other adjacent wavelength spectrums--typically radiation having a wavelength in the range of between 10 and 15,000 nm.)
An optical resonator is a major component of many different optical devices. For example, the lasing cavity of a laser is, in essence, an optical resonator--lasing is amplification and oscillation of optical radiation between reflective surfaces in a resonant fashion. A swept-tuned spectrum analyzer also utilizes a resonator capable of frequency tuning. Second harmonic generators, optical parametric oscillators, and other non-linear optical converters represent other instruments which can make usage of resonators. The applications of resonators are quite wide-ranging.
Often one of the dominant goals in designing resonators for most instruments is to provide as high a Finesse (or a high quality factor) as is practical. The Finesse of a particular resonator typically is deduced from measurements taken on the resonator. (Finesse can, of course, also be estimated.) It can be thought of as a measurement of efficiency, i.e., the enhancement of the optical power of the resonant field compared to the power fed into the resonator.